VITAL STAINING AND MORPHOGENETIC MOVEMENTS 



211 



Presumptive maps of (a) the young Composite drawing to illustrate germ -layer relations 

 gastrula of Triton (Vogt, '29); in the late gastrulo of an Anuron. Medullary plate 



(b) the early blastula of Triton (ectoderm) not indicated. 



(Vogt, '29); (c) of the young gastrula Alternate dots and dashes - endoderm 



of Triturus pyrrhogaster (Nakamura, Heavy stippling - notochord 



'38). Sparse stippling - mesoderm 



Cellular markings - ectoderm 



Schematic representation indicating 

 on the map the position of the parts 

 of an anterior trunk segment (a) and 

 of a posterior trunk segment (b). 



(From Pasteels, 1942: Jour. Exp. 

 Zool. 89:255) 



OBSERVATIONS AND DATA 



This is strictly a qualitative, observational type of experiment and it will be necessary 

 to keep separate and periodic records of each stained egg or embryo. The significance 

 of the experiment will depend upon the accuracy and the completeness of the record. The 

 embryos should be kept in Standard Solution, in separate #2 Stenders, properly marked 

 for identification. When the dye is moved internally, it can be traced by dissection of 

 the living embryo. It must be remembered, however, that the dyes are soluble and some 

 will diffuse out of the embryo and also into surrounding cell areas. 



It is possible to preserve the Nile blue sulphate for histological examination by using the 

 following procedure: (Stone, 1932) 



a. Fix in Zenker s-acetic for 2 hours. 



b. Wash in tap water. 



c. Place in 1% Phosphomolybdic acid for 2 hours. 



d. Transfer to dioxan to which 0. 1% Phosphomolybdic acid has been added - for 2 

 two-hour changes. 



e. Transfer to cedar oil plus 0. 1% Phosphomolybdic acid until clear. 



f. Embed in paraffin, 3 baths of about 15 minutes each. 



g. Section and mount in xylol-clarite. 



(It is the Phosphomolybdic acid which keeps the Nile blue sulphate in position. ) 



^y "All these observations taken together illustrate enipliatically the integration of all 

 gastrulation movements , the uniformity of the process as a whole, wliose basic trends -- 

 elongation, convergence, divergence, etc. -- transcend the border lines of invagiiwting 

 and non-invaginating areas and of the prospective germ layers. " Hamburger 1960, p. 59. 



